ENCLOSING DAMS. 



43 



each separate caisson was of cast iron, weighing about 32 cwt., 

 with a cutting edge at its lowest extremity so as the more 

 readily to penetrate the soil. 



In order to form a water-tight joint between the caissons at 

 their junctions, a cast-iron groove 5J inches deep and 6J inches 



wide, was bolted to the flanges at the end of each caisson, so that 

 when the several portions or sections were placed in position 

 each groove came opposite to that of the contiguous one, and 

 thus formed an aperture 10 \ inches long by 6J inches wide from 



